The preview
The Preview tab shows your app live, as your visitors will see it. It runs in an isolated environment dedicated to your project, and updates with every file the agent writes: you watch the app grow section by section while it works. You can click, fill in forms and move between pages just like on the real site.
The preview bar
Section titled “The preview bar”Above the app, from left to right:
| Item | What it does |
|---|---|
| Desktop · Tablet · Mobile | Changes the screen size. Desktop takes the full width; Tablet shows the app in a 768 × 1024 px frame (a tablet in portrait); Mobile in a 390 × 844 px frame (a phone). If there isn’t enough room, the frame is scaled down: the app keeps its real width. |
| Address bar | Shows the current page (/, /pricing…). Click it, type a path and press Enter to open that page; Esc cancels. The dot on the left turns green when the preview is ready. |
| Reload | Reloads the page on screen. |
| Server logs | Opens the logs panel at the bottom of the preview (see below). |
| Open in a new tab | Opens the page on screen in a new browser tab, full screen. |
The first generation: the build screen
Section titled “The first generation: the build screen”When the agent builds a new app, the preview shows a Highwind is building your app screen: “The preview shows up as soon as the page is ready.” It lists the latest files written and what the agent is doing (“Analysing the project…”, “Writing code…”, “Thinking…”). As soon as the app’s first page exists, the screen fades out and you watch the app fill in live.
When the app runs into an error
Section titled “When the app runs into an error”If the app crashes or shows a blank page, a banner appears at the bottom of the preview: The app ran into an error (or N errors), with the type of error and its message.
- Click Details to see all the errors (type, message and file involved).
- Click Fix: Highwind sends the agent a message with the errors (“The preview shows an error. Please fix it: …”), in Building mode. The agent analyses them and fixes the code.
- Or click Dismiss (the cross) to hide the banner, if the error doesn’t bother you for now.
The kinds of errors reported are: Exception (the code crashed), Unhandled rejection (an asynchronous operation failed), console.error (the code wrote an error to the console), Compilation (the code doesn’t compile) and Blank page (nothing shows up).
Good to know:
- While the agent is working, the banner is hidden: the agent sees the preview’s errors itself and fixes them before it finishes.
- On an old version there’s no Fix button (an old version can’t be changed).
- Fix is a request to the agent like any other: it uses credits and creates a new version.
Server logs
Section titled “Server logs”If your app has a server (/api routes, to send emails, call a service with a key…), its logs help you understand what’s going on. Click Server logs in the preview bar: a panel opens at the bottom, with two tabs.
- Preview: the logs of the preview’s development server. You see your app’s
console.logoutput and/apiroute errors, as well as Vite’s messages. Error lines are in red. The panel refreshes every two seconds and sticks to the bottom, unless you scroll up to read. - Live: the logs of your published app, over the last 24 hours, a few seconds late. Each
/apicall shows with its time, its result (status code) and its duration, along withconsole.logoutput and errors.
Messages you may see there:
| Message | Meaning |
|---|---|
| “Nothing yet…” | The server hasn’t written anything yet. Use the feature in the preview to generate logs. |
| “The preview is asleep: logs will resume when it wakes up.” | The preview environment went to sleep (see below). |
| “This app isn’t published yet…” | Live tab: publish the app to get live logs. |
| “The published app has no server (static site)…” | Live tab: your app has no /api routes, so there are no logs. |
The Server logs button only shows on the current version, not when you view an old version.
Sleep and wake-up
Section titled “Sleep and wake-up”So environments don’t run for nothing, the preview goes to sleep after a while without activity. Your files are kept.
- As long as the editor tab is open and visible, Highwind regularly signals your activity: the preview stays awake.
- When you come back to the tab (or reopen the project), the preview wakes up on its own: “Starting the preview…” shows for a few seconds, then the app is back.
- If starting fails, an error message shows with a Retry button.
Previewing an old version
Section titled “Previewing an old version”When you view an old version from the history, the preview shows “Preparing version N…” while a temporary environment starts with that version’s code. You can move around the app, but not change it or select elements. See Versions and history.